Global health impacts of ambient fine particulate pollution associated with climate variability

Air pollution is a key global environmental problem raising human health concern. It is essential to comprehensively assess the long-term characteristics of air pollution and the resultant health impacts. We first assessed the global trends of fine particulate matter (PM2.5) during 1980-2020 using a monthly global PM2.5 reanalysis dataset, and evaluated their association with three types of climate variability including El Niño-Southern Oscillation, Indian Ocean Dipole and North Atlantic Oscillation. We then estimated PM2.5-attributable premature deaths using integrated exposure-response functions. Results show a significant increasing trend of ambient PM2.5 during 1980-2020 due to increases in anthropogenic emissions. Ambient PM2.5 caused a total of ∼ 135 million premature deaths globally during the four decades. Occurrence of air pollution episodes was strongly associated with climate variability, which were associated with up to 14 % increase in annual global PM2.5-attributable premature deaths.

Using routine blood parameters to anticipate clinical outcomes in invasive aspergillosis

OBJECTIVE

In invasive aspergillosis (IA), monitoring response to antifungal treatment is challenging. We aimed to explore if routine blood parameters help to anticipate outcomes following IA.

METHODS

Post hoc secondary analysis of two multicenter randomized trials was performed. The Global Comparative Aspergillosis Study (GCA, n = 123) and the Combination Antifungal Study (CAS, n = 251) constituted the discovery and validation cohorts respectively. The outcome measures were response to treatment and survival to 12 weeks. Interval platelet, galactomannan index (GMI) and C-reactive protein (CRP) levels prior and during antifungal treatment were analysed using logistic regression, Kaplan-Meier survival and receiver operating characteristic (ROC) analyses.

RESULTS

The 12-week survival was 70.7% and 63.7% for the GCA and CAS cohorts respectively. In the GCA cohort, every 10 × 10⁹/L platelet count increase at week 2 and 4 improved 12-week survival odds by 6-18% (odds ratio (OR) 1.06-1.18, 95% confidence interval (CI) 1.02-1.33). Survival odds also improved 13% with every 10 mg/dL CRP drop at week 1 and 2 (OR 0.87, 95% CI 0.78-0.97). In the CAS cohort, week 2 platelet count was also associated with 12-week survival with 10% improved odds for every 10 × 10⁹/L platelet increase (OR, 1.10, 95% CI 1.04-1.15). A GMI drop of 0.1 unit was additionally found to increase the odds of treatment response by 3% at the baseline of week 0 (OR 0.97, 95% CI 0.95-0.99). Week 2 platelet and CRP levels performed better than GMI on ROC analyses for survival (area under ROC curve 0.76, 0.87 and 0.67 respectively). A baseline platelet count higher than 30 × 10⁹/L clearly identified patients with >75% survival probability.

CONCLUSIONS

Higher serial platelets were associated with overall survival while GMI trends were linked to IA treatment response. Routine and simple laboratory indices may aid follow-up of response in IA patients.

The Long-Term Impact of Functional Disability on Hospitalization Spending in Singapore

Singapore is one of the fastest-aging populations due to increased life expectancy and lowered fertility. Lifestyle changes increase the burden of chronic diseases and disability. These have important implications for social protection systems. The goal of this paper is to model future functional disability and healthcare expenditures based on current trends. To project the health, disability and hospitalization spending of future elders, we adapted the Future Elderly Model (FEM) to Singapore. The FEM is a dynamic Markov microsimulation model developed in the US. Our main source of population data was the Singapore Chinese Health Study (SCHS) consisting of 63,000 respondents followed up over three waves from 1993 to 2010. The FEM model enables us to investigate the effects of disability compounded over the lifecycle and hospitalization spending, while adjusting for competing risk of multi-comorbidities. Results indicate that by 2050, 1 in 6 elders in Singapore will have at least one ADL disability and 1 in 3 elders will have at least one IADL disability, an increase from 1 in 12 elders and 1 in 5 elders respectively in 2014. The highest prevalence of functional disability will be in those aged 85 years and above. Lifetime hospitalization spending of elders aged 55 and above is US$24,400 (30.2%) higher among people with functional disability compared to those without disability. Policies that successfully tackle diabetes and promote healthy living may reduce or delay the onset of disability, leading to potential saving. In addition, further technological improvements may reduce the financial burden of disability.

Study of the electronic structure of the interfaces between 2-TNATA and MoOx

In order to understand the characteristics of ohmic hole-contacts for the inverted/conventional organic light emitting devices, a hole-only device with all ohmic contacts, which is composed of glass/ITO/MoOx/4,4,4-tris[2-naphthyl-phenyl-amino]triphenylamine (2-TNATA)/MoOx/Al, the elements of the electronic structures of MoOx-on-2-TNATA interface and 2-TNATA-on-MoOx interface were investigated by photoemission spectroscopy, with regards to interface energetics, formative mechanism, and a potential charge carrier injection. The electronic structures revealed that the behavior of the interface between MoOx and 2-TNATA was different whether MoOx was deposited on (2-TNATA) or vice versa. The bottom interfaces of 2-TNATA-on-MoOx in this hole-only devices showed no hole-injecting barrier height (Phi(h)B) when the thickness of 2-TNATA was deposited in the range of 0.1 to 5.0 nm on the 10.0 nm-thick MoOx thin films. This has been explained to be attributed to both metal-induced gap states and a chemical reaction at the interfaces. The top interfaces of MoOx-on-2-TNATA in this hole-only device structure also showed no Phi(h)B when a hole was injected from the MoOx-on-2-TNATA interfaces to cathode. The hole-ohmic property in the top interfaces depends on interface dipole by the formation of charge transfer complexes as well as interdiffusion of MoOx into the 2-TNATA film in these interfaces.

Oral steroids enhance epithelial repair in nasal polyposis via upregulation of the AP-1 gene network

BACKGROUND

Chronic mucosal inflammation, epithelial damage and aberrant tissue remodelling are common features in nasal polyposis (NP). A study was undertaken to characterise the gene expression profile in NP tissues and to explore the molecular mechanisms underlying the ameliorative effects of glucocorticosteroids (GCs) in NP.

METHODS

Two sets of NP biopsies (before and after GC treatment) were taken from 10 patients with untreated (GC-naïve) bilateral NP. Biopsy specimens of inferior turbinate from 6 patients who underwent surgery for nasal septal deviation served as nasal mucosal controls. DNA microarrays containing 38 500 genes were used to characterise the global gene expression profile. Functional network analysis was applied to identify the key molecular pathways and genes in response to GC treatment (GC-treated). Selected genes were retested by quantitative RT-PCR and immunohistochemistry in the same polyps and control samples.

RESULTS

64 genes were differentially expressed in GC-treated vs GC-naïve NP tissues. The highest scoring network was assembled around activation protein 1 (AP-1), a heterodimer of c-Fos and c-Jun oncoprotein, and five AP-1-related genes (COX-2, IL-6, AREG, HBEGF and EGR1) with tissue repair function. Quantitative PCR confirmed that AP-1 and its related genes were markedly repressed in GC-naïve polyps and were upregulated after GC treatment. Immunohistochemical staining indicated that epithelial restitution in GC-treated polyps was associated with increased expression of c-Jun protein.

CONCLUSIONS

Oral steroids promote epithelial repair in NP via upregulation of the AP-1 (especially c-Jun) network and its related genes.

Malignant melanoma seen in a tertiary dermatological centre, Singapore

INTRODUCTION

Primary malignant melanoma is an uncommon skin tumour in Singapore compared with the Western countries. The clinical characteristics of melanoma have been rarely reported in Asians.

OBJECTIVES

Our purpose was to study the incidence, clinical characteristics and risk factors of biopsy proven malignant melanoma seen in a tertiary referral skin hospital.

METHODS

Case records of patients with histology proven malignant melanoma from January 1989 to December 1998 were retrieved. Patients were interviewed and a complete skin and systemic examination was performed. Data on demographics, histological types, clinical characteristics and risk factors were collated.

RESULTS

Between 1989 and 1998, 27 patients were diagnosed with histology proven malignant melanoma. There was a predominance of Chinese with a female to male ratio of 1.3:1. There was a mean lag period of 1.6 years to diagnosing melanoma and there is a general lack of knowledge among the local patients. Most of the lesions (89%) occurred on the extremities. Acral lentiginous melanoma (41%) and nodular melanoma (41%) were the two commonest histologic types. Of the nodular melanomas, 64% were observed in patients below 50 years (64%) while majority of the acral lentiginous melanomas occurred in those above 50 years (91%). In terms of risk factors, we reported a high prevalence of diabetes mellitus with acral lentiginous melanoma.

CONCLUSIONS

This study highlighted interesting aspects in terms of clinical characteristics and risk factors in our local patients. It also served as a remainder of the need to raise awareness among the public and medical community of skin cancers or melanomas as they are potentially treatable if detected early.

Treatment with a copper-zinc chelator markedly and rapidly inhibits beta-amyloid accumulation in Alzheimer's disease transgenic mice

Inhibition of neocortical beta-amyloid (Abeta) accumulation may be essential in an effective therapeutic intervention for Alzheimer's disease (AD). Cu and Zn are enriched in Abeta deposits in AD, which are solubilized by Cu/Zn-selective chelators in vitro. Here we report a 49% decrease in brain Abeta deposition (-375 microg/g wet weight, p = 0.0001) in a blinded study of APP2576 transgenic mice treated orally for 9 weeks with clioquinol, an antibiotic and bioavailable Cu/Zn chelator. This was accompanied by a modest increase in soluble Abeta (1.45% of total cerebral Abeta); APP, synaptophysin, and GFAP levels were unaffected. General health and body weight parameters were significantly more stable in the treated animals. These results support targeting the interactions of Cu and Zn with Abeta as a novel therapy for the prevention and treatment of AD.

Evidence that the beta-amyloid plaques of Alzheimer's disease represent the redox-silencing and entombment of abeta by zinc

Abeta binds Zn(2+), Cu(2+), and Fe(3+) in vitro, and these metals are markedly elevated in the neocortex and especially enriched in amyloid plaque deposits of individuals with Alzheimer's disease (AD). Zn(2+) precipitates Abeta in vitro, and Cu(2+) interaction with Abeta promotes its neurotoxicity, correlating with metal reduction and the cell-free generation of H(2)O(2) (Abeta1-42 > Abeta1-40 > ratAbeta1-40). Because Zn(2+) is redox-inert, we studied the possibility that it may play an inhibitory role in H(2)O(2)-mediated Abeta toxicity. In competition to the cytotoxic potentiation caused by coincubation with Cu(2+), Zn(2+) rescued primary cortical and human embryonic kidney 293 cells that were exposed to Abeta1-42, correlating with the effect of Zn(2+) in suppressing Cu(2+)-dependent H(2)O(2) formation from Abeta1-42. Since plaques contain exceptionally high concentrations of Zn(2+), we examined the relationship between oxidation (8-OH guanosine) levels in AD-affected tissue and histological amyloid burden and found a significant negative correlation. These data suggest a protective role for Zn(2+) in AD, where plaques form as the result of a more robust Zn(2+) antioxidant response to the underlying oxidative attack.

3-Hydroxykynurenine and 3-hydroxyanthranilic acid generate hydrogen peroxide and promote alpha-crystallin cross-linking by metal ion reduction

The kynurenine pathway catabolite 3-hydroxykynurenine (3HK) and redox-active metals such as copper and iron are implicated in cataractogenesis. Here we investigate the reaction of kynurenine pathway catabolites with copper and iron, as well as interactions with the major lenticular structural proteins, the alpha-crystallins. The o-aminophenol kynurenine catabolites 3HK and 3-hydroxyanthranilic acid (3HAA) reduced Cu(II)>Fe(III) to Cu(I) and Fe(II), respectively, whereas quinolinic acid and the nonphenolic kynurenine catabolites kynurenine and anthranilic acid did not reduce either metal. Both 3HK and 3HAA generated superoxide and hydrogen peroxide in a copper-dependent manner. In addition, 3HK and 3HAA fostered copper-dependent alpha-crystallin cross-linking. 3HK- or 3HAA-modifed alpha-crystallin showed enhanced redox activity in comparison to unmodified alpha-crystallin or ascorbate-modified alpha-crystallin. These data support the possibility that 3HK and 3HAA may be cofactors in the oxidative damage of proteins, such as alpha-crystallin, through interactions with redox-active metals and especially copper. These findings may have relevance for understanding cataractogenesis and other degenerative conditions in which the kynurenine pathway is activated.

Separation of related opiate compounds using capillary electrochromatography

Capillary electrophoretic separations have been investigated for six controlled narcotic analgesic compounds having related structures. Owing to the similar charge-to-mass ratios of these compounds, capillary zone electrophoresis failed to provide a satisfactory separation, whereas a baseline-resolved separation was achieved in 10 min using micellar electrokinetic chromatography. Column efficiencies of 40,000-150,000 plates/m were obtained with a 50 cm long, 50 microm inner diameter (ID) capillary using 50 mM sodium dodecyl sulfate (SDS) in a 50 mM borate solution containing 12% isopropanol. In contrast, separation of this mixture by capillary electrochromatography proved to be significantly superior. The capillary was 15 cm long, with an ID of 75 microm, and was packed with 1.5 microm nonporous octadecyl silica (ODS) particles. The mobile phase consisted of 80% 10 mM tris(hydroxymethyl)aminomethane (Tris) and 20% acetonitrile, and contained 5 mM SDS. A complete separation was obtained in 2.5 min with an efficiency of 250,000-500,000 plates/m.

Primary chemo-radiotherapy and selective oesophagectomy for oesophageal cancer: goal of cure with organ preservation

PURPOSE

The role of definitive chemo-radiotherapy in squamous cell oesophageal carcinoma has been established by the Radiation Therapy Oncology Group (RTOG). We have studied a modification of the RTOG chemo-radiotherapy protocol in patients with any histologic type of oesophageal carcinoma. We planned oesophagectomy for patients with post-treatment positive endoscopic biopsy or <75% regression on CAT scan, or with resectable local recurrence. Study end-points were histologic response, toxicity, oesophagectomy and survival rates after primary chemo-radiotherapy.

METHODS

Consecutive patients with any T or N status, M0, disease encompassable in radical radiotherapy ports, no prior surgical excision, and fit for chemo-radiotherapy, were eligible. Treatment plan was three cycles of cisplatin/5-fluorouracil chemotherapy and radical external radiation therapy (50 Gy in 25 fractions) starting with cycle 2. Selective oesophagectomy was performed in patients with post-treatment positive biopsy or <75% regression on CT scan, or with localized recurrence.

RESULTS

From 1993-1996, 32 patients were treated. Post-treatment complete histologic response rate was 77% (95% confidence limits 58-90%). Grade 3 or 4 toxicities occurred in 31 and 3 patients, respectively. Minimum follow-up time was 12 months. Median disease-specific survival time was 16.1 months for all patients, and was not significantly different according to histologic type (17 squamous, 12 adenocarcinoma). Oesophagectomy was performed in six of 15 surviving and five of 17 deceased patients.

CONCLUSION

It is possible to cure oesophageal cancer with chemo-radiotherapy and selective oesophagectomy, and achieve organ preservation in the majority of long term survivors.

Neoadjuvant hormone therapy and external beam radiation for localized prostate cancer: Vancouver Island Cancer Centre experience

OBJECTIVES

To evaluate the effects of neo-adjuvant hormone therapy (NAHT) given prior to radiation in patients with clinically localized adenocarcinoma of the prostate.

METHODS

Six hundred nine patients were treated between 1992 and 1997 with NAHT prior to radiation therapy. Clinical stage, presenting PSA and Gleason score were examined for influence on outcome. Time to post radiotherapy failure was defined from the first assessed PSA value over 4 microg/L at follow-up. Radiation therapy was confined to the prostate and seminal vesicles. Median follow-up was 2.6 years.

RESULTS

PSA disease free survival (PDFS) decreased with increasing cancer risk factors (p <.0.0001). The overall duration of NAHT was significant with patients receiving >8 months having a lower failure rate than those on therapy for <3 months (p <0.0001). The PSA prior to starting radiation correlated with outcome, a PSA <=0.1 microg\L having a better PDFS than those with a PSA >=4 microg\L (P <0.0001). NAHT for >8 months gave improved PDFS in intermediate grade Gleason score 5-7, (n = 256, p <0.0001), high grade Gleason score 8-10 (n = 80, p =0.005), but not in low grade, Gleason score <=4.

CONCLUSION

Neo-adjuvant hormone therapy for >8 months offers prolonged PSA disease free survival in patients with less well differentiated tumors, Gleason score >4. Clinical trials are required to confirm this.

Repigmentation of vitiligo with autologous blister-induced epidermal grafts

Treatment of vitiligo can sometimes be difficult and disappointing. PUVA treatments give fairly good results. However, acral regions like the hands or feet or areas over bony prominences like the elbow, are resistant to PUVA. Blister-induced epidermal grafts have been used to repigment vitiligo skin. This study was carried out on patients with vitiligo areas unresponsive to either PUVA treatments or who had segmental vitiligo. PUVA treatments were resumed after skin grafting. Twenty-five patients with stable vitiligo were grafted with blister-induced epidermal grafts. Up to 70% of the whole vitiligo areas were grafted in one sitting. A total of 105 grafts were done. In 9 grafts, no repigmentation was seen. The remaining 96 grafts resulted in pigmentation. Twelve had partial and 84 had complete repigmentation. No Koebner phenomenon was noted in both the recipient sites or the donor sites. Blister-induced epidermal graft is an effective alternative to repigment stable vitiligo areas. It is easy to do and results are good. In this study, 96 out of 105 (91%) grafts had repigmentation.

Sulindac derivatives inhibit growth and induce apoptosis in human prostate cancer cell lines

We examined the activity of two metabolites of sulindac (a nonsteroidal anti-inflammatory drug), sulindac sulfide and sulindac sulfone (exisulind, Prevatec), and a novel highly potent analog of exisulind (CP248) on a series of human prostate epithelial cell lines. Marked growth inhibition was seen with the BPH-1, LNCaP, and PC3 cell lines with IC50 values of about 66 microM, 137 microM, and 64 nM for sulindac sulfide, exisulind, and CP248, respectively. DNA flow cytometry and 4',6'-diamido-2-phenylindole (DAPI) staining indicated that these three compounds also induced apoptosis in all of these cell lines. Similar growth inhibition also was seen with the PrEC normal human prostate epithelial cell line, but these cells were resistant to induction of apoptosis at concentrations up to 300 microM, 1 mM, and 750 nM of sulindac sulfide, exisulind, and CP248, respectively. Derivatives of LNCaP cells that stably overexpress bcl-2 remained sensitive to growth inhibition and induction of apoptosis by these compounds. In vitro enzyme assays indicated that despite its high potency in inhibiting growth and inducing apoptosis, CP248, like exisulind, lacked cyclooxygenase (COX-1 and COX-2) inhibitory activity even at concentrations up to 10 mM. Moreover, despite variations of COX-1 and COX-2 expression, the three benign and malignant prostate cell lines showed similar sensitivity to growth inhibition and induction of apoptosis by these three compounds. Therefore, sulindac derivatives can cause growth inhibition and induce apoptosis in human prostate cancer cells by a COX-1 and -2 independent mechanism, and this occurs irrespective of androgen sensitivity or increased expression of bcl-2. These compounds may be useful in the prevention and treatment of human prostate cancer.

The therapeutic efficacy of mometasone furoate cream 0.1% applied once daily vs clobetasol propionate cream 0.05% applied twice daily in chronic eczema

BACKGROUND

Mometasone furoate [9a, 21-dichloro-llb, 17dihydroxy-16a-methyl-pregna-14-dione-3, 20-dione-17-(2furoate)] is a synthetic, 17-heterocyclic corticosteroid which has been shown to be highly effective as an anti-inflammatory agent which is approximately half as potent is suppressing hypothalamic-pituitary-adrenal (HPA) axis function as betamethasone valerate.

METHOD

The present open, randomised, third party blinded, left-right sided study was designed to compare the therapeutic efficacy of mometasone furoate cream 0.1% with clobetasol propionate cream 0.05% applied twice daily in chronic eczema following a 3-week course of therapy.

PATIENTS/RESULTS

Sixty consecutive patients with moderate to severe bilateral chronic eczema on the limbs were recruited into the study. The mean scores of various signs/symptoms including erythema, induration, crusting, scaling, excoriation and pruritus before and after 3 weeks treatment with mometasone furoate (MF) and clobetasol propionate (CP) cream, were compared. The baseline scores for MF and CP treated sites were almost identical. There was significant decrease in the mean scores of all signs/symptoms after 3 weeks treatment with MF and CP. There was also a significant difference in the mean scores between MF and CP treated sites after 3 weeks of treatment. The mean scores were significantly lower for CP treated sites than MF treated sites. More CP treated sites achieved "cleared" or "marked improvement" response than MF treated sites. There were more "excellent" or "good" grades on CP treated sites than MF treated sites at the end of 3 weeks of treatment. None of the patients showed any side-effects after 4 weeks of treatment.

CONCLUSION

Overall, 53% of patients considered the MF treated sites to be good or excellent vs 88% for CP treated sites.

Retrospective study of Behcet's disease seen at the National Skin Centre, Singapore

This retrospective study characterises the clinical manifestations and outcome of 34 patients diagnosed with Behcet's disease seen at the National Skin Centre from 1990 to 1997. The 2 diagnostic criteria used were the International Study Group and the O'Duffy criteria. Seventy-six per cent satisfied both criteria and the remaining 24% satisfied only the incomplete form of the O'Duffy criteria. We found that the male to female ratio was 1:1.8. The mean age of presentation was 33 years (range 21 to 63 years). The majority were Chinese (73%). In our series, patients had prominent mucocutaneous involvement. These findings may be attributed to patient selection to a tertiary dermatology clinic. Oral (100%) and genital (99%) ulceration were the 2 commonest symptoms. The other cutaneous features included papulo-pustular or acneiform eruption (26%), erythema nodosum (14.7%) and positive pathergy test. Five patients (15%) had arthritis, 1 patient had recurrent thrombophlebitis and 2 patients had eye complications. The outcome of our patients was generally good with minimal functional impairment and no mortality detected. Our patients were primarily outpatient referrals and this may explain why systemic complications were rare in our series.

Treatment of melasma using kojic acid in a gel containing hydroquinone and glycolic acid

BACKGROUND

Melasma is difficult to clear. Many agents have been used, such as hydroquinone, and glycolic acid and glycolic acid peels, kojic acid, a tyrosinase inhibitor in the fungus Aspergilline oryzae.

OBJECTIVE

To see if the addition of 2% kojic acid in a gel containing 10% glycolic acid and 2% hydroquinone will improve melasma further.

METHODS

Forty Chinese women with epidermal melasma were treated with 2% kojic acid in a gel containing 10% glycolic acid and 2% hydroquinone on one half of the face. The other half was treated with the same application but without kojic acid. The side receiving the kojic acid was randomized. Determination of efficacy was based on clinical evaluation, photographs and self-assessment questionnaires at 4 weekly intervals until the end of the study at 12 weeks. The non-parametric Wilcoxon's rank sum test was used for statistical analysis.

RESULTS

All patients showed improvement in melasma on both sides of the face. The side receiving the kojic acid did better. More than half of the melasma cleared in 24/40 (60%) patients receiving kojic acid compared to 19/40 (47.5%) patients receiving the gel without kojic acid. In 2 patients, there was complete clearance of melasma, and this was on the side where kojic acid was used. Side effects include redness, stinging, and exfoliation. These were seen on both sides of the face, and they settled by the third week.

CONCLUSION

The addition of kojic acid to a gel containing 10% glycolic acid and 2% hydroquinone further improves melasma.

Cutaneous vasculitis seen at a skin referral centre in Singapore

OBJECTIVE

To study the clinical features and course of patients presenting to a skin referral centre with cutaneous vasculitis.

METHOD

A retrospective review of patients presenting to the National Skin Centre from 1993 to 1995 with cutaneous vasculitis was done. All patients included in the study had histologically proven vasculitis on skin biopsy. The clinical manifestations and laboratory investigations of the patients were recorded. The response to the various drugs given as first line therapy and course of the disease 1 year after initial presentation was reviewed.

RESULTS

Forty-seven patients were included in this study. Females outnumbered males in a ratio of approximately 2:1 (32 females versus 15 males). The age of the patients ranged from 14 to 78 years, with a mean of 36 years. The aetiology remained elusive in 70% of cases. Of the known secondary causes, drugs and streptococcal infections were the most frequently implicated. The lower limbs were involved in more than 90% of cases. Cutaneous lesions took the form of palpable purpura, ulcers, nodules and urticaria. Extracutaneous manifestations were present in 47% of patients. The main extracutaneous manifestations were arthralgia/arthritis (21%), microscopic haematuria (16%) and abdominal pain (8%). Direct immunofluorescence on lesional skin was positive in 65% of cases. A raised erythrocyte sedimentation rate was observed in 40% of patients. Positive antinuclear antibodies were detected in 30% of cases. Most patients who were given systemic corticosteroids responded predictably well. The response to other modalities of treatment was more variable. At 1 year follow-up, complete remission was recorded in 47% of the patients, while in 53% of the patients, the disease continued to run a chronic relapsing course.

Comparative effects of overexpression of p27Kip1 and p21Cip1/Waf1 on growth and differentiation in human colon carcinoma cells

Recent studies have shown that decreased expression of p27Kip1 is associated with high grade tumors and an unfavorable prognosis in several types of human cancer. To clarify the role of p27Kip1 in colon cancer, we have overexpressed this protein in the HT29 colon cancer cell line. The derivatives displayed an increase in the p27Kip1 protein in cyclin E/CDK2 immunoprecipitates and a decrease in cyclin E-associated kinase activity when compared to vector control clones, providing evidence that the overexpressed protein was functional. Clones with a high level of p27Kip1 displayed partial growth inhibition in monolayer culture and a decrease in plating efficiency, even though they expressed increased levels of the cyclin D1 protein. Using alkaline phosphatase expression as a marker, we found that the p27Kip1 overexpressor clones displayed a 2-3-fold increase in sensitivity to induction of differentiation by 2 mM sodium butyrate. In contrast to these results, derivatives of HT29 cells that stably overexpressed p21Cip1/Waf1 displayed decreased sensitivity to the induction of differentiation. These findings may explain why decreased levels of p27Kip1 in certain human cancers is associated with high grade (poorly differentiated) tumors, and suggest that strategies that increase the level of p27Kip1 may be useful in cancer therapy.

Cyclin D1 expression in human prostate carcinoma cell lines and primary tumors

BACKGROUND

The cyclin D1 gene is amplified and/or overexpressed in several types of human cancer, including cancers of the breast, esophagus, head, and neck. However, the role of cyclin D1 in prostate cancer has not been previously studied in detail.

METHODS

Six human prostate cancer cell lines and cultures of normal human prostate cells were examined by Western and Northern blot analyses for levels of expression of the cyclin D1 protein and mRNA, respectively. Southern blot analyses were performed to examine possible amplification of this gene. Immunostaining for cyclin D1 was performed on 50 primary prostate cancer samples.

RESULTS

Cyclin D1 protein was expressed at relatively high levels in all of the six human prostate cancer cell lines examined, but was not detected in the cultures of normal human prostate cells. The ALVA 41 cell line expressed the highest level of this protein. Relatively high levels of cyclin D1 mRNA were also found in all of the prostate cancer cell lines. Nevertheless, none of these cell lines revealed amplification of the cyclin D1 gene. Twelve of the 50 primary prostate cancer samples (24%) revealed regions of moderate to strongly positive staining for cyclin D1.

CONCLUSIONS

The increased expression of cyclin D1 in several prostate cancer cell lines and in a subset of primary prostate cancer samples suggests that further studies on the expression of this gene and related genes may be of interest in understanding the pathogenesis of prostate cancer.

Effects of sulindac and its metabolites on growth and apoptosis in human mammary epithelial and breast carcinoma cell lines

Nonsteriodal anti-inflammatory drugs (NSAIDs) are among the most commonly used medications in the United States and elsewhere, mainly for the treatment of arthritis. The NSAID sulindac causes regression and prevents the recurrence of premalignant colonic polyps in patients with familial adenomatous polyposis and inhibits colon carcinogenesis in rodents. Sulindac and sulindac sulfone, a metabolite of sulindac that lacks cyclooxygenase (cox) inhibitory activity, also inhibit mammary carcinogenesis in rats. To obtain insights into the relevance of these findings to human breast cancer, we examined the mechanism of action of sulindac and its sulfide and sulfone metabolites on the normal human mammary epithelial cell line MCF-10F and the human breast cancer cell line MCF-7. Of the three compounds, the sulfide was the most potent inhibitor of cell growth, although the sulfone and sulfoxide were also active at higher concentrations. Treatment of MCF-10F and MCF-7 cells with 100 microM sulindac sulfide resulted in accumulation of cells in the G1 phase of the cell cycle and induction of apoptosis. Apoptosis occurred within 24 h as determined by the TUNEL assay and DNA laddering was observed at 72 h. The accumulation of cells in G1 was associated with decreased levels of expression of cyclin D1 but no effect was seen on the expression of CDK4 or the immediate early response gene c-jun. Treatment with sulindac sulfide caused a striking induction of the CDK inhibitor p21WAF1 in MCF-10F cells. The MCF-7 cell line expressed a high basal level of p21WAF1 which did not change significantly after drug treatment. The pro-apoptotic gene BAX was not induced in either MCF-10F or MCF-7 cells by sulindac sulfide. Stable overexpression of cyclin D1, which frequently occurs in breast cancers, did not protect mammary epithelial cells from inhibition by the sulfide. These studies suggest that this class of compounds warrants further study with respect to breast cancer prevention and treatment.

Induction of micronuclei in human, goat, rabbit peripheral blood lymphocytes and mouse splenic lymphocytes irradiated in vitro with gamma radiation

The frequencies of gamma-ray-induced micronuclei (MN) in cytokinesis-blocked (CB) lymphocytes at several doses were measured in three donors of four species (human, goat, rabbit, mouse). Measurements performed after irradiation showed a dose-related increases in MN frequency in each of the donors studied. The relative sensitivity of mouse in spleen lymphocytes (SLs), goat in peripheral blood lymphocytes (PBLs) and rabbit PBLs compared with human PBLs was estimated by best fitting linear-quadratic model based on the radiation-induced MN data over the range from 0 to 400 cGy. In the case of MN frequency with 0.2, the relative sensitivities of mouse SLs, goat PBLs and rabbit PBLs were 1.67, 0.98 and 0.39, respectively. These data indicate that the induction of MN in CB cells following irradiation is similar in human and goat PBLs, and PBLs from rabbit were much less sensitive to the MN induction effects of gamma-radiation than those from human. Compared with the radiation-induced MN formation in the PBLs of human, the SLs of mouse were more radiosensitive.

Glycolic acid peels in the treatment of melasma among Asian women

BACKGROUND

Melasma is a common disorder of facial hyperpigmentation among Asian women. Many modalities of treatment are available but none is satisfactory.

OBJECTIVE

This study was undertaken to see if glycolic acid peels are effective and safe in the treatment of melasma and fine facial wrinkling.

METHODS

Ten Asian women with moderate to severe melasma were recruited into the study. The women had twice daily applications of a cream containing 10% glycolic acid and 2% hydroquinone (Neostrata AHA Age Spot and Skin Lightening Gel) to both sides of the face, and glycolic acid peels every 3 weeks (20-70%) to one-half of the face using Neostrata Skin Rejuvenation System. All patients had to use a sunblock (SPF 15%). At regular intervals and at the end of 26 weeks (or after eight peels) the degree of improvement of pigmentation and fine facial wrinkling on each side of the face were assessed. Any skin irritation or side effects were also noted. Assessment was by an independent dermatologist, the patients themselves, and the use of the Munsell color chart and photographs. The nonparametric Wilcoxon Rank-Sum test was used for statistical analysis.

RESULTS

The melasma and fine facial wrinkling improved on both sides of the face. The side that received glycolic acid peels did better but the results were not statistically significant (P > 0.059).

CONCLUSION

A cream containing 10% glycolic acid and 2% hydroquinone (Neostrata AHA Age Spot and Skin Lightening Gel) improved melasma and fine facial wrinkling in Asian women. In combination with glycolic acid peels at 3-week intervals the lightening of melasma is subjectively much better. This improvement does not reach statistical significance and the sample size is small (n = 10).

Dimerization of a chimeric CD4-interferon-alpha receptor reconstitutes the signaling events preceding STAT phosphorylation

Interferon-alpha induces the rapid tyrosine phosphorylation of a number of molecules, including the cognate receptors, JAK-family kinases (Jak1 and tyk2), and latent transcription factors (STATs 1 and 2). Here, we describe the use of chimeric molecules composed of the extracellular domain of CD4 fused to the intracellular domain of the interferon-alpha receptor subunit 1 (IFNaR1). Antibody mediated crosslinking dimerizes the transfected chimeras, activates tyk2 and induces a tyk2-dependent tyrosine phosphorylation of the intracellular domain of the chimera. We further define the major site of IFNaR1 phosphorylation, and show that phosphorylation of this site is required for association with STAT2. Finally, we show that homodimerization of IFNaR1 is not sufficient to activate the STATs, suggesting a role for the IFNaR2 subunit and Jak1 in the transduction of the interferon-alpha signal.

Molecular characterization of an alpha interferon receptor 1 subunit (IFNaR1) domain required for TYK2 binding and signal transduction

Binding of alpha interferon (IFNalpha) to its receptors induces rapid tyrosine phosphorylation of the receptor subunits IFNaR1 and IFNaR2, the TYK2 and JAK1 tyrosine kinases, and the Stat1 and Stat2 transcription factors. Previous studies have demonstrated that TYK2 directly and specifically binds to and tyrosine phosphorylates IFNaR1 in vitro. We now report a detailed analysis of the TYK2 binding domain on the IFNaR1 subunit. First, we used an in vitro binding assay to identify the TYK2 binding motif in IFNaR1 as well as the critical residues within this region. The most striking feature is the importance of a number of hydrophobic and acidic residues. A minor role is also ascribed to a region resembling the proline-rich "box 1" sequence. In addition, mutations which disrupt in vitro binding also disrupt the coimmunoprecipitation of the receptor and TYK2. We also provide direct evidence that the binding region is both necessary and sufficient to activate TYK2 in vivo. Specifically, mutations in the binding domain act in a dominant-negative fashion to inhibit the IFNalpha-induced tyrosine phosphorylation of TYK2 and Stat2. Further, introduction of dimerized glutathione S-transferase-IFNaR1 fusion proteins into permeabilized cells is sufficient to induce phosphorylation of TYK2 and the receptor, confirming the role of the binding domain in IFNalpha signal transduction. These studies provide clues to the sequences determining the specificity of the association between JAK family tyrosine kinases and cytokine receptors as well as the functional role of these kinases in cytokine signal transduction.

Phosphorylated interferon-alpha receptor 1 subunit (IFNaR1) acts as a docking site for the latent form of the 113 kDa STAT2 protein

Interferon-alpha (IFN alpha) induces rapid tyrosine phosphorylation of its receptors, two JAK kinases and three STAT transcription factors. One kinase, p135tyk2, is complexed with the IFNaR1 receptor, and may catalyze some of these phosphorylation events. We demonstrate that, in vitro, p135tyk2 phosphorylates two tyrosines on IFNaR1. A phosphopeptide corresponding to the major phosphorylation site (Tyr466) binds STAT2, but not STAT1, in an SH-2-dependent manner. Furthermore, only latent, non-phosphorylated STAT2 interacts with this phosphopeptide. When this phosphopeptide is introduced into permeabilized cells, the IFN alpha-dependent tyrosine phosphorylation of both STATs is blocked. Finally, mutant versions of IFNaR1, in which Tyr466 is changed to phenylalanine, can act in a dominant negative manner to inhibit phosphorylation of STAT2. These observations are consistent with a model in which IFNaR1 mediates the interaction between JAK kinases and the STAT transcription factors.

An unusual drug eruption to ampicillin

The authors describe an unusual presentation of ampicillin allergy. A 24-year-old Chinese man noted localized pustular skin eruptions on his cheeks each time he ingested ampicillin. These eruptions would subside spontaneously within a week after stopping use of ampicillin. Drug provocation with ampicillin reproduced the same eruption in exactly the same sites. The eruptions were different clinically and histologically from fixed drug eruptions. The mechanism of such eruption is unknown.

Technical optimization of spiral CT for depiction of renal artery stenosis: in vitro analysis

PURPOSE

To determine empirically the effect of scan parameters and postprocessing techniques on depiction accuracy of renal artery stenosis with spiral computed tomographic angiography.

MATERIALS AND METHODS

Critical (85%) and noncritical (45%) stenoses in the coronal plane were modeled in vitro and scanned with 12 combinations of collimation (1, 2, or 3 mm), table increment (pitch = 1-2),2 and reconstruction interval (0.5 or 1.0 mm). Five test images were generated for each spiral scanning technique: multiplanar reformation (MPR), maximum-intensity projections (MIPs: coronal MIP [MIPcor], coronal MIP targeted to phantom vessel and surrounding fat [target MIPcor]), transaxial imaging, and transaxial MIP.

RESULTS

With 3-mm collimation, critical stenosis was overestimated to the point of occlusion on MIPcor images and underestimated on MPR and target MIPcor images. A 0.5-mm reconstruction interval was marginally beneficial for 1- and 2-mm collimation, but noise was prohibitive with 1-mm collimation.

CONCLUSION

Critical renal artery stenosis is best depicted with 2-mm collimation, 2-4-mm table increment, and 1-mm reconstruction interval.

Methotrexate in the treatment of psoriasis at the National Skin Centre, Singapore

In the last 30 years, methotrexate has been used for treating psoriasis, rheumatoid arthritis and other inflammatory disorders. Much has been learned about its beneficial and adverse effects. Long-term use produces different effects from short-term use. This study was undertaken to study the long-term use of methotrexate in our local population. It is a retrospective study where the case reports of 72 psoriatic patients on methotrexate were analysed for its use, side effects, the monitoring of side effects and its efficacy. Our study showed that methotrexate was effective in 61 (86.0%) patients, had some side effects in 10 (14.2%) patients and was relatively safe. It also helped psoriatic arthropathy. However, adequate and close monitoring is required to prevent liver fibrosis and cirrhosis.

Lasers used in dermatology

This review introduces the various lasers available for the treatment of dermatological conditions. The applications of various lasers used in dermatology, including the carbon dioxide, argon, Q-switch Nd:YAG, ruby, dye and metal vapour lasers are discussed. We present our experience with the use of the carbon dioxide laser, flashlamp pulse-dye laser and Q-switch Nd:YAG laser in the National Skin Centre, Singapore. Our experience indicated that the lasers if used selectively are useful tools in the management of numerous skin disorders. The carbon dioxide laser is a versatile tool, useful for vaporizing or destroying skin lesions. The treatment of vascular or pigmented (melanin) lesions requires lasers that emit wavelengths corresponding to the absorption spectrum of haemoglobin or melanin respectively. Choosing the right laser gives optimal cosmetic result whereas the wrong lasers can lead to a less satisfactory result and even severe scarring. It is important to note that there is no single laser system that is versatile enough to be used to treat all skin disorders. To provide full coverage in the treatment of skin disorders, a laser centre has to be equipped with many different laser systems. This makes using lasers in the treatment of skin disorders very expensive.

Efficacy and safety of multidrug therapy in paucibacillary leprosy in Singapore

A total of 49 patients with paucibacillary leprosy (PB) who completed multidrug therapy (MDT) between 1985 and 1990 were analysed retrospectively for efficacy and complications; 20 (40.8%) patients had borderline-tuberculoid (BT), 13 (26.5%) had tuberculoid (TT), 1 (2.1%) had indeterminate (I) and 15 (30.0%) had pure neural (N) leprosy; 26 patients (76.5% of 34 non-neural leprosy) were skin biopsied for histological cure before MDT was stopped. Of these 26 patients, 19 had histological clearance at 6 months while the remaining 7 cleared beyond 1 year (18-36 months). The remaining 8 non-neural patients who refused rebiopsy had MDT for 6-8 months and the MDT was stopped when there was clinical clearance. Of the 15 neural (N) leprosy patients, 11 were given MDT for 6 months while the rest had 12-18 months of treatment; 1 patient with neural leprosy, who was treated for 6 months, relapsed with BT leprosy 18 months post-treatment. There were few complications among the 49 patients-4 (8.2%) patients developed reaction to dapsone, 1 (2.0%) had the dapsone syndrome, 2 (4.1%) had haemolytic anaemia and 1 (2.0%) had dapsone hepatitis; 7 (14.3%) patients had type I reaction.

Neoadjuvant carboplatin and ifosfamide chemotherapy for inoperable FIGO stage III and IV ovarian carcinoma

Thirty patients aged 34-69 years (median 56) with previously untreated FIGO Stage III and IV ovarian carcinoma were given carboplatin (400 mg/m2) and ifosfamide (5 g/m2) with mesna every 28 days for a median of 3 cycles, followed, where possible, by laparotomy. Objective responses were observed in 13 (43%) patients, 11 of whom proceeded to laparotomy. Nine were successfully debulked, and two of these had removal of all macroscopic disease. Three cycles of chemotherapy were found to achieve the optimum response for the least toxicity. After a minimum follow-up of 32 months, two patients who had had debulking surgery remain alive. The median response duration was 13.9 months in the debulked group compared with 3 months in those who remained inoperable, while the corresponding median survivals were 23.4 and 6.4 months. This study suggests that neoadjuvant chemotherapy given over 8 weeks may render debulking surgery feasible in a proportion of patients presenting with unresectable ovarian cancer and can result in an improved median survival.

Dermatophyte and non-dermatophyte onychomycosis in Singapore

Onychomycosis is caused by dermatophytes, moulds and yeasts. It is important to identify the non-dermatophyte moulds as they are resistant to the usual anti-fungals. A prospective study was undertaken in the National Skin Centre, Singapore to study the pattern of dermatophyte and non-dermatophyte onychomycosis. 53 male and 47 female patients seen between June 1990 and June 1991 were entered into the study. Direct microscopy was done and the nail clippings were cultured. Toe and finger nails were equally infected. Dermatophytes were isolated from 21 patients namely, T. rubrum (12/21), T. interdigitale (5/21), T. mentagrophytes (3/21) and T. violaceum (1/21). Candida onychomycosis occurred in 39 patients and was caused by C. albicans (38/39) and C. parapsilosis (1/39). 37/39 patients had associated paronychia. 5 types of moulds were isolated from 12 patients, namely Fusarium species (6/12), Aspergillus species (3/12), S. brevicaulis (1/12), Aureobasilium species (1/12) and Penicillium species (1/12). Although the clinical pattern and microscopy may predict the type of organisms, in practice this is difficult. Only cultures were confirmatory. 28% (28/100) had negative cultures despite a positive microscopy, and moulds (12/100) grown might be contaminants rather than pathogens.

Pattern of dermatophyte infection in Singapore

Dermatophyte infection is the fourth commonest skin disorder seen in the National Skin Centre in Singapore. A prospective study was carried out from June 1990 to March 1991 to determine the epidemiology and pattern of dermatophyte infections seen in this centre. Two hundred patients who had a clinical diagnosis of dermatophyte infection and confirmed by direct microscopy were included into the study. Cultures for dermatophyte were done on Sabouraud's dextrose agar with chloramphenicol and cycloheximide. There were 148 male and 52 female patients, of whom 146 (73%) had a positive culture from one or more sites. One hundred and thirty-nine (95.2%) patients had dermatophyte infection while the remaining seven (4.8%) patients had non-dermatophyte infection. The sites involved were the groin (92 patients), feet (52 patients), trunk (26 patients), hands (18 patients), face (9 patients), legs (9 patients), scalp (8 patients) and axilla (7 patients). The commonest dermatophyte isolated was Trichophyton rubrum (81/139). It was also the commonest organism isolated in all the sites except the scalp. The other dermatophytes grown were, in order of frequency, Trichophyton interdigitale (21/139), Epidermophyton floccosum (19/139), Trichophyton mentagrophytes (9/139), Microsporum ferrigineum (4/139), Microsporum canis (4/139) and Microsporum gypseum (1/139). Scalp infections occurred in children and were due either to Microsporum canis or Microsporum ferrigineum. The organisms isolated in our study were either ubiquitous or common in the Asia-Pacific region indicating that certain dermatophytes are more prevalent in certain geographical regions.

Carbon dioxide laser treatment of periungual and subungual viral warts

This is a retrospective study of the cure rates of forty patients with subungual and periungual viral warts treated with carbon dioxide laser vapourisation (total of 69 lesions). 70.6% (48/68) lesions had failed treatment with cryotherapy and/or electrocautery treatment previously. 20/68 were treated with CO2 laser vapourisation as a first line treatment. The overall cure rate over 10 months follow-up period was 57.4% (39/68). Most recurrences (24/25) occurred within the first 3 months of vapourisation. The carbon dioxide laser vapourisation cure rate for warts in which previous cryotherapy and/or electrocautery had failed was 47.9% whereas those treated with carbon dioxide laser vapourisation as a first line treatment had a cure rate of 80% (p = 0.043). Subungual warts responded slightly better with a cure rate of 64.7% compared with periungual warts (54.9%) (n.s.). The carbon dioxide laser vapourisation cure rate for recurrent subungual and periungual warts (which failed previous carbon dioxide laser vapourisation) was 73.3% (11/15). Our findings appeared to indicate that periungual and subungual warts can be eradicated by CO2 laser vapourisation. Recurrent warts can be effectively eradicated by further vapourisation. Recalcitrant periungual and subungual warts which have previously failed to respond to cryotherapy and/or electrocautery can be effectively eradicated with CO2 laser vapourisation.

Irradiation of the pinna with superficial kilovoltage radiotherapy

Excellent local control can be achieved by treating superficial carcinomas of the skin with superficial kilovoltage radiotherapy. The results of this study support the use of 100-140 KV photons to treat carcinomas of the skin of or around the pinna. This achieves a local control rate of 97% and the radionecrosis rate of 10% could be halved if all patients were treated with 3500 cGy in 5 fractions over one week, or to a maximum area of 5 cm2 of irradiated pinna. An audit of the running cost reveals that this method of treating superficial carcinomas is highly cost effective and can be recommended for all suitable patients.

Changing trends in the epidemiology of contact dermatitis in Singapore

All patients seen in the Contact Dermatitis Clinic of the National Skin Centre, Singapore (and the former Middle Road Hospital) between January 1986 and December 1990 were analysed retrospectively. 5557 patients comprising 2634 (47.4%) males and 2923 (52.6%) females were patch tested. 3154 (56.8%) patients had 1 or more positive reactions. The majority of the patients were Chinese (78.0%), followed by Malays (11.5%), Indians (8.1%) and other minority races (2.4%). The majority of positive reactions belonged to the 21-40 age group. The incidence of positivity decreased after 60 years. The commonest allergens responsible were nickel (17.7%), fragrance (13.3%), neomycin (6.9%), colophony (6.6%) and proflavine (6.5%). Both neomycin and proflavine were commonly used as over-the-counter medicaments. Compared to an earlier report in 1988, there were differences in the incidence of contact sensitivity to some allergens. Potassium dichromate, which used to be a common allergen, was less common. Some allergens (carba-mix, naphthyl-mix, caine-mix and PCMX) have been removed from our standard series as they were uncommon causes of contact allergy. Thimerosal and Amerchol L-101 were added in their place.

Fixed drug eruptions due to co-trimoxazole

Co-trimoxazole is a less common cause of fixed drug eruption (FDE). The offending drug is usually sulfamethoxazole but reactions to trimethoprim have been reported. Fixed drug eruption is uncommon in children compared to adults as the drugs most commonly responsible are seldom or never used in children. We report four patients with FDE to co-trimoxazole, three of whom were children. All were given the offending drug for upper respiratory tract infections. Each of the patients had several episodes of FDE before the diagnosis was suspected. The patients, as well as the general practitioners, initially thought that the skin lesions were related to the infections rather than the drugs. One of the patients had FDE to trimethoprim and the intensity of his reaction appeared to be dose-related. As co-trimoxazole is being used more commonly, we would expect to see more FDE, even among the paediatric age group.

Pityriasis rubra pilaris in Singapore

Fourteen patients with pityriasis rubra pilaris seen between 1981 and 1989 were evaluated retrospectively. There were nine male and five female patients. There was a bimodal age of onset in early childhood and in adulthood. All the patients had either follicular hyperkeratosis or hyperkeratosis of the palms and soles. Nine patients had erythroderma. The classical forms, either in the children or in the adult patients, were more likely to recover. Several treatment modalities were used and these included steroids, Vitamin A, etretinate, retinoic acid and ultraviolet light (UBV). Nine patients had complete recovery. Four of these patients received only steroids, two cleared while on vitamin A, two cleared while on etretinate and one cleared with methotrexate.

The changing patterns of scabies among in-patients in Singapore (1982-1989)

One hundred and fourteen patients with scabies admitted to a dermatological ward between 1982 and 1989 were studied retrospectively. There was a change in the epidemiological pattern over the eight-year period. We noticed an increase of two to three fold in the incidence of in-patients with scabies. At the beginning of the decade the majority of the patients were below 20 years but towards the end of the decade the same proportion of patients were above 50 years. There was also a change in the racial distribution of scabies from a Malay predominance to a Chinese predominance. We also noticed a change in the residential status of these patients; more patients admitted towards the end of the decade came from institutional homes. The changing epidemiological pattern brought with it new problems both in diagnosis and in the prevention of scabies.

Coexisting follicular mucinosis and mycosis fungoides--a case report

This is a case report of a patient with mycosis fungoides coexisting with follicular mucinosis. The simultaneous occurrence of these two conditions has been documented. There is controversy as to whether mycosis fungoides in patients with follicular mucinosis arises de novo or whether follicular mucinosis can evolve into mycosis fungoides. The relationship between the two conditions is discussed.

A dynamic growth model of vegetative soya bean plants: model structure and behaviour under varying root temperature and nitrogen concentration

A differential equation model of vegetative growth of the soya bean plant (Glycine max (L.) Merrill cv. Ransom') was developed to account for plant growth in a phytotron system under variation of root temperature and nitrogen concentration in nutrient solution. The model was tested by comparing model outputs with data from four different experiments. Model predictions agreed fairly well with measured plant performance over a wide range of root temperatures and over a range of nitrogen concentrations in nutrient solution between 0.5 and 10.0 mmol NO3- in the phytotron environment. Sensitivity analyses revealed that the model was most sensitive to changes in parameters relating to carbohydrate concentration in the plant and nitrogen uptake rate.

A Monte Carlo/response surface strategy for sensitivity analysis: application to a dynamic model of vegetative plant growth

We describe the application of a strategy for conducting a sensitivity analysis for a complex dynamic model. The procedure involves preliminary screening of parameter sensitivities by numerical estimation of linear sensitivity coefficients, followed by generation of a response surface based on Monte Carlo simulation. Application is to a physiological model of the vegetative growth of soybean plants. The analysis provides insights as to the relative importance of certain physiological processes in controlling plant growth. Advantages and disadvantages of the strategy are discussed.

Incorporation of measured photosynthetic rate in a mathematical model for calculation of non-structural saccharide concentration

A simple mathematical model for calculating the concentration of mobile carbon skeletons in the shoot of soya bean plants [Glycine max (L.) Merrill cv. Ransom] was built to examine the suitability of measured net photosynthetic rates (PN) for calculation of saccharide flux into the plant. The results suggest that either measurement of instantaneous PN overestimated saccharide influx or respiration rates utilized in the model were underestimated. If neither of these is the case, end-product inhibition of photosynthesis or waste respiration through the alternative pathway should be included in modelling of CH2O influx or efflux; and even if either of these is the case, the model output at a low coefficient of leaf activity indicates that PN still may be controlled by either end-product inhibition or alternative respiration.